1. Technical Field
The present invention relates to a vertical alignment correction apparatus and method and more particularly, to a vertical alignment correction apparatus and method for a bidirectional scanner device.
2. Related Art
Multimedia systems that are driven to present combinations of moving and still pictures, sound, music, and words, are pervasive in the industrialized world, especially in computers or in other entertainment appliances. Concurrent with the development of multimedia computer systems, peripheral equipment including image formation equipment such as printers, have been incrementally modified to provide various functions. A multi-tasking system, employing an ink-jet mechanism and serving as a facsimile and scanner, will typically be coupled to an external personal computer that performs a user-selected program and generates print data. The multi-tasking system typically either receives data from the personal computer or scan data printed on the exposed surface of one or more documents. Conventional multi-tasking systems include a scanner such as a laser flatbed or sheetfed scanner, for reading information existing on a document by scanning the document. With a sheetfed laser scanner, the scanner remains in a fixed state while the document bearing the information is moved in a vertical direction during laser scanning of its exposed surface. With a flatbed laser scanner, a laser beam is swept across a flat plate by the scanner modulated by video signals from a similar reading system or by digital signals generated by a computer.
A conventional scanner is designed to convert images recorded on a document into a computer-compatible electronic form. The images recorded on the document can be scanned as follows. An amount of light is first transmitted to the document from a source. As a result, the image data on the document causes some of that light to be reflected in a particular pattern. The pattern of reflected light is then supplied to a fixed array of light sensors through an intermediate image reduction mirror. The light sensors in the array can be charge-coupled devices (CCD) or contact image sensors (CIS). Then circuitry in the scanner senses the status of each sensing element in the array one by one, in order, to register the brightness of each point in each individual scan line. After the scanner has collected and arranged the data from each sensor, the next line of data can be read. Image data read from a document can be recorded onto a recordable medium. Image data read from a document can be considered as scanned data or scan data.
There are two main categories of conventional scanner devices: the shuttle type and the array type. The array type shall be considered first. The array type of scanner scans the data recorded on the document per a line unit, when a line scanner module having a size similar to, or larger than, the width of the document is fixed at a predetermined position inside of the multifunctional device. The scanner module is typically stationary while the document is transported along a path of conveyance through the scanner device.
The shuttle type of scanner can be described as follows. The shuttle type of scanner typically has a guide axis, a transporting belt, and a driving source for driving the transporting belt, which are all established at the scanning unit, in order to reciprocate the scanner module perpendicular to the document transporting direction. Thus, the scanner module is typically transported back and forth along a first path while the document is transported along a second path through the scanner device, the first and second paths being perpendicular to one another. Some shuttle type scanners are unidirectional and some are bidirectional. Unidirectional shuttle type scanners read image data from a document only while the scanner module is being transported in a first direction along the first path. Bidirectional shuttle type scanners read image data from a document while the scanner module is being transported in a first direction along the first path and also while the scanner module is being transported in a second direction along the first path.
I have found that unidirectional shuttle type scanners often read image data at a slower rate than bidirectional shuttle type scanners. However, image data read by unidirectional scanners typically have fewer alignment problems than do the image data read by bidirectional scanners.
I have discovered that it would be desirable to develop an enhanced bidirectional scanner having improved image data reading capabilities such that speed is increased and alignment problems are reduced.